An organic EL display device (Organic Electroluminescence Display) is known as one type of display device. In the organic EL display device, an organic electroluminescence material (organic EL material) is used in a light emitting element (organic EL element) which is included in each pixel of a display part. Unlike a liquid crystal display device or the like, an organic EL display device is a so-called self-light emitting type display device which realizes display by making an organic EL material emit light.
In an organic EL display device, each light emitting element generally has an organic layer including a light emitting layer between a pixel electrode and an opposing electrode. Here, an organic EL material is used for the light emitting layer. When a potential difference of 10V or more, for example, is applied to the pixel electrode and the opposing electrode, a current flows between the pixel electrode and the opposing electrode and the organic EL material emits light. For example, the light emitting layer is selectively formed for each pixel using a vapor deposition mask. In the case when an improvement of productivity and a reduction of production costs is considered, it is desirable that layers other than the light emitting layer in the organic layer are formed in common for each pixel. However, for example, when a hole injection layer (HIL) which is one of the organic layers is used commonly between each pixel, since resistivity of the hole injection layer is low, a current also flows to pixels other than a desired pixel. This current is called a leak current, a horizontal direction leak current, or a lateral leak current (referred to as a first leak current in the present specification). When the first leak current flows, pixels other than the desired pixel emit light. As a result, in the organic EL display device, the light emitting efficiency of the display device or the light emitting element decreases. In addition, color mixture occurs in the organic EL display device. As a result, image quality of the display device sometimes decreases. In addition, when a potential difference of less than 10V, for example, about 2V is applied to the pixel electrode and the opposing electrode of the desired pixel, a leak current (also referred to as a horizontal direction leak current or lateral leak current) occurs in the vicinity of a light emitting layer (referred to as a second leak current in the present specification). Due to the second leak current, the light emitting efficiency of the display device or the light emitting element may decrease.
For example, a structure in which adjacent pixels are unintentionally controlled to emit light by a first leak current is disclosed in Japanese Laid Open Patent Publications 2016-103395 and 2016-085913.